And speaking of past hardcore ventures, my absolute worst was when I was playing my Hell sorceress in Diablo2 and was about to do Duriel (the cold/poison larva at the end of act2, in the tombs). I used the staff on the pedestal, the wall opened up, I cast a town portal to go back and refill my potions and check my gear, and I misclick the entrance to the boss room instead of the portal. I had no rejuvenation pots and died as I scrambled to cast another town portal. I just rested my head on the edge of my desk while letting out the deepest groan.

Oh man, I think I might have the ultimate hardcore mode death or at least the most prolonged one...

I was playing a druid and had pretty crazy health. I think I was about level 70. I was on hell difficult in hell (the lava area right before Diablo's chamber). I had about 20 rejuvenation pots but a pretty crappy melee weapon, so my damage was terrible - just had no luck replacing it. I stumbled into a giant mass of enemies that were mostly those big blunderbore guys. I started fighting and they began closing in around me, so, at the last moment, while there was still a narrow path of escape, I went to back out to avoid being trapped. There was a fucking skull or some other tiny object on the ground that somehow blocked pathing even though it was barely visible. My escape was cut off and they totally closed in around me. I tried opening portals but they were all just out of reach... so then I started hacking away and drinking potions in what was probably the slowest hardcore mode death ever. Because my weapon sucked and they were such high-hp enemies, it was just taking forever to kill them. I had my inventory open that started out almost entirely full of rejuvs and just kept chugging. It seriously took about 15mins for me to finally run out of potions and I was down to only about 1 layer of enemy before I could cut through and escape but, alas, I just couldn't kill them fast enough and finally died.